Coordinated Control of Multiple Dynamic VAR Sources in LCC-HVDC Systems to Mitigate Commutation Failure and Enhance Voltage Stability

With the increasing share of renewable energy in modern power systems, high-voltage direct current (HVDC) transmission plays a pivotal role in enabling long-distance, high-capacity power transfer. However, during such large-scale long-distance transmission, HVDC systems may experience faults such as commutation failure or DC blocking, which can lead to severe voltage fluctuations on the AC side and pose significant threats to overall system security and stability. To address the dual challenges of limited response speed and insufficient capacity in existing static reactive power compensation devices, this paper proposes a multi-dynamic reactive power source coordinated control strategy. By comprehensively leveraging synchronous condensers, STATCOMs, capacitor banks, and filters through hierarchical coordination and priority-based scheduling, the proposed approach ensures efficient reactive power support during both transient and steady-state periods of converter station faults. Comparative analyses of typical scenarios on an electromagnetic transient simulation platform demonstrate that, compared with employing a single dynamic reactive power compensator, the multi-source coordinated control not only provides rapid and sufficient reactive support during faults—significantly mitigating voltage spikes or dips—but also effectively shortens voltage recovery time and reduces the risk of commutation failure. This study offers substantial engineering value for enhancing voltage stability and transmission capacity in AC-DC hybrid grids under high renewable penetration.